Rihanna, JWoww, and more stars with sexy bikini selfies

What big change happens on social media between spring and summer? Those selfies that celebs are so fond of posting suddenly show a lot more skin! (No complaints here!) We've collected pics from the stars who have stripped down to their tiniest bikinis, picked up their smart phones, and are showing off their sexiest self-portraits. Enjoy!RELATED:Video: Best bikini TwitPics"My girl! @erinmccarley" --Hayden Panettiere, who took a sexy selfie with singer Erin McCarley and proved, once and for all, that two bikini-clad hotties are better than one!